Standard dipstick tests for UTI miss over 60% of infections

GPs rely on dipstick tests to diagnose UTIs. But these tests are seriously flawed. Research shows dipsticks have a 70% inaccuracy rate (see also here) causing some to suggest it should be abandoned as a diagnostic tool. New research found that dipstick tests miss at least 60% of infections in patients with persistent or chronic infections.

Relying on flawed tests have serious consequences for patients. When dipstick tests fail to identify an infection, doctors and urologists can dismiss bacterial infection and look for other causes. With an infection ruled out, patients often then undergo painful and invasive investigations to find another cause.

How do dipstick tests work?

GP analysis of a urine sample involves a dipstick test before any urine laboratory analysis is carried out. A standard urine test strip may comprise up to 10 different chemical pads which react (change colour) when immersed in, and then removed from, a urine sample. The test can often be read in as little as 1-2 minutes after dipping, although some tests require longer.

The analysis includes testing for the presence of proteins, blood, nitrites and leukocytes (white blood cells), all symptoms of urinary tract infections. Urine dipsticks were first developed for commercial use in the late 50s/early 60s.

Read more about how to interpret your urine dipstick test

What are the problems with dipstick tests?

Negative dipstick analysis is common even though the patient has described UTI symptoms.  This can be due to the following:

Dipsticks – the case against

Research in the last 20 years has shown that whilst they can identify acute infections, it is low growth bacterial infections where they become unreliable.  One study noted: “The nitrite test performs particularly badly and leukocyte esterase achieved a sensitivity of only 59%”.1, 2

What to avoid if you need to provide a urine sample:

  • Dilution of the sample by drinking too much liquid (the first urination of the day when you wake up or acidic, concentrated urine is best for analysis). If this is not possible, limit fluids for around three – four hours before providing your sample so it isn’t too dilute.
  • Usage of previous antibiotics to treat a recent infection. Ideally you need to be off antibiotics for around 7-10 days to clear the medication from your system before providing another urine sample. Usage of antibiotics may inhibit bacterial growth resulting in a negative result even if you still have symptoms.
  • If you are using D-Mannose or other natural herbal supplements to treat your infections stop at least 48 hours before testing.
  • Urinary painkillers such as Azo should be stopped 24 hours before a sample as this medication type can affect results.
  • Diuretics should also be stopped as well as Vitamin C – all can lead to false negative results.

References

1. The Inadequacy of Urinary Dipstick and Microscopy as Surrogate Markers of Urinary Tract Infection in Urological Outpatients with Lower Urinary Tract Symptoms Without Acute Frequency and Dysuria: Rajvinder Khasriya, Shozab Khan, Rahul Lunawat, Samuel Bishara, Jenine Bignal, Matthew Malone-Lee, Hiro Ishii, Dominic O’Connor, Michael Kelsey and James Malone-Lee J Urol. 2010 May;183(5):1843-7. doi: 10.1016/j.juro.2010.01.008.

2. Reliability of dipstick assay in predicting urinary tract infection. Mambatta, A. K., Jayarajan, J., Rashme, V. L., Harini, S., Menon, S., & Kuppusamy, J. (2015). Journal of Family Medicine and Primary care, 4(2), 265-8.